|Publication number||US7012214 B2|
|Application number||US 10/669,858|
|Publication date||Mar 14, 2006|
|Filing date||Sep 24, 2003|
|Priority date||Sep 24, 2003|
|Also published as||CA2539579A1, EP1673193A1, US20050061785, WO2005080042A1|
|Publication number||10669858, 669858, US 7012214 B2, US 7012214B2, US-B2-7012214, US7012214 B2, US7012214B2|
|Inventors||Kurt A. Schroder, Doug K. Jackson|
|Original Assignee||Nanotechnologies, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (17), Non-Patent Citations (2), Referenced by (8), Classifications (18), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
In the present invention, further improvements are made in the synthesis of nanopowders by applying a high intensity magnetic field to electrodes of precursor material during the time that an electrical discharge arc is generated between the electrodes. Higher production yields thereby are attained than that achievable by the above prior art nanopowder synthesizing systems. Further improvement is obtained if a magnet insert of coating precursor material is used to reduce agglomeration of the nanopowder particles.
The invention relates generally to nanopowder synthesis processes, and more particularly to the use of an applied magnetic field to significantly increase nanopowder production rates resulting from a synthesis process.
Plasma based systems for synthesizing nanopowders are disclosed in U.S. Pat. Nos. 5,514,349; 5,874,684; and 6,472,632. The axial electrothermal gun embodiment disclosed in U.S. Pat. No. 6,472,632 is an improvement over the plasma based synthesis systems of the '349 and '684 patents. The '632 system uses a high powered pulsed arc discharge in combination with an axial electrothermal gun to attain a higher temperature and higher density of the plasma that is not ordinarily attainable by the other plasma based synthesis systems. The higher temperature and higher density provides a higher production rate of nanopowder.
A still further improvement in nanopowder production is provided by the nanopowder synthesis system disclosed in U.S. patent application Ser. No. 10/455,292, which issued as U.S. Pat. No. 6,777,639. Referring to
A reoccurring problem in the above prior art systems is that the arc discharge may occur from time to time at other than the center of the electrodes. In this event, the resistance of the discharge arc is decreased, and less energy may be added to the arc discharge for a given arc current. The plasma that is created thus may be of a lower temperature and/or lower density than otherwise could be attained. As a result, production rates are decreased, and the material produced is of a non-uniform quality.
FIG. 4 of U.S. patent application Ser. No. 10/455,292, which issues as U.S. Pat. No. 6,777,639, discloses a composite electrode embodiment of the above radial gun, where the electrodes are each seated within hollow ablative bodies to form composite electrodes. Although the discharge arc may emanate from the edges of the anode and cathode electrodes, it will remain near the center of the composite electrodes to approach the high temperatures and high densities that otherwise would be available if the discharge arc emanated from the centers of the anode and cathode electrodes.
In the present invention, further improvements are made in the synthesis of nanopowders by applying a high magnetic field to electrodes of precursor material during the time that an electrical discharge arc is generated between the electrodes. Higher production yields thereby are attained than that achievable by the above prior art nanopowder synthesizing systems. Further improvement is obtained if a magnet insert of coating precursor material is used to reduce agglomeration of the nanopowder particles.
While the novel aspects and features of the invention are defined in the appended claims, the principles of the invention, illustrative embodiments, and preferred modes of use are best understood by reference to the Detailed Description Of Preferred Embodiments in conjunction with the following drawings, in which:
The following terms shall have the definitions given below when used in either lower case or with capitalizations in this specification.
“Nanopowder” shall mean nanomaterial primarily comprised of nanoparticles which are of a size of 1–500 nanometers (nm).
“Ablative Material” shall mean material removed from a body of precursor material due to the combined effects of heat transfer and mechanical shear caused by plasma velocities.
“Precursor Material” shall mean material which is processed to produce nanopowder.
“Coating Precursor Material” shall mean material which is processed to produce a coating on the nanopowder.
“Radial Gun” shall mean a device wherein a pulsed arc discharge occurs between two opposing electrodes composed of a precursor material. The electrodes are substantially axially aligned opposite to each other within a gaseous atmosphere. The term “radial gun” is used for convenience only, and is not meant to imply any limitation of the present invention.
“High Intensity Magnetic Field” shall mean a magnetic field in the range of 0.50 or more Tesla.
“High Power” shall mean power of the order of 100 kWatts or more.
Same reference numbers used in the description of the invention which follows will refer to same devices, whether or not they appear in more than one drawing.
The solenoid magnet 22 is a magnet which creates a high intensity magnetic field principally along its major axis. The magnetic field may be varied by varying the power supplied to the magnet. Alternatively, the number of windings, or the diameter of the windings of the magnet could be altered to vary the magnetic field.
Two electrodes 24 a and 24 b composed of precursor material are slidably inserted through pneumatic seals 25 a and 25 b. The electrodes 24 a and 24 b are axially aligned but spaced apart in opposing relation. The solenoid magnet 22 is axially aligned with the electrodes 24 a and 24 b, and positioned uniformly around the electrodes to overlap the gap between the electrodes.
The solenoid magnet 22 may be purchased from any of numerous well known manufacturers of custom designs including Everson Tesla Inc. of Nazarath, Pa., and Cryogenics Limited of London, United Kingdom.
Gas sources 26 a and 26 b respectively supply reaction gas and quenching gas by way of gas conduits 27 a and 27 b, and gas valves 28 a and 28 b, to gas conduit 29. The gas conduit 29 in turn extends through and is in pneumatically sealed relation with the outer surface of the reaction chamber 21.
The positive terminal of a pulsed power supply 30 is connected by way of a conducting wire 31 to a first terminal of a pulse forming network 32, the second terminal of which is connected by way of a conducting wire 33 to the end of the electrode 24 a which is exterior to the reaction chamber 21. The negative terminal of power supply 30 is connected by way of a conducting wire 34 to the end of electrode 24 b which is exterior to the reaction chamber 21. Output terminals of a charging power supply 35 are connected by way of conducting wires 36 a and 36 b to input terminals of the pulsed power supply 30.
The positive and negative terminals of pulsed power supply 37 respectively are connected by way of conducting wires 38 a and 38 b to electrodes of the solenoid magnet 22. The input terminals of the pulsed power supply 37 are respectively connected by way of conducting wires 39 a and 39 b to output terminals of a charging power supply 40.
The main pulsed power supply 30 of
A trigger input terminal of pulsed power supply 30 is connected by way of a fiber optic cable 41 to a first output terminal of a timing control system 42, the second output terminal of which is connected by way of a fiber optic cable 43 to the trigger input terminal of pulsed power supply 37.
The intake port of a blower 44 is connected to a conduit 45 leading to the output of a filter 46 located within a collection vessel 47. The output port of the blower 44 is connected to a conduit 48 leading to an intake port 49 of the reaction chamber 21. An output port 50 of the reaction chamber 21 is connected to a conduit 51 leading to an input port of the collection vessel 47.
The conically shaped bottom of the collection vessel 47 tapers inward to an isolation valve 52 which is connected to a collection jar 53 for collecting filtered nanopowder particulates.
In operation, one or more of the gas valves 28 a and 28 b are opened to respectively allow desired amounts of reaction gas from gas source 26 a and quenching gas from gas source 26 b to enter the reaction chamber 21. The gas is recirculated by the blower 44 in the closed loop system comprising the reaction chamber 21, conduit 51, collection vessel 47, conduit 45, and conduit 48. The charging power supplies 35 and 40 are energized to respectively charge the pulsed power supplies 30 and 37. The timing control system 42 thereupon is operated to trigger pulsed power supply 30 and pulsed power supply 37 in a timed relation which ensures that a high power pulsed electrical discharge arc occurs between the electrodes 24 a and 24 b in the presence of a pulsed, high intensity magnetic field. The corresponding pulsed plasma created by the ablation of the electrodes 24 a and 24 b reacts/quenches with the gas to form nanopowder. The nanopowder in turn flows out of the reaction chamber 21, through the conduit 51, and into the collection vessel 47. The filter 46 acts to filter out the nanopowder which is subsequently collected in the collection jar 53.
The timing control system 42 is set to allow the pulsed power supplies 30 and 37 to become fully charged before they are triggered. It has been found that the timing of the trigger pulses to the pulsed power supplies 30 and 37 directly affect the nanopowder production rate. Referring to
It is to be understood that while
Continuing with the description of
The strength of the magnetic field produced by the magnet 22 may be determined from equations well known in the magnet design art, and is a function of the number and geometry of the windings, the input current, and the magnetic permeability of any matter between the windings and the point at which the field is measured. If the magnet is pulsed, electrical conductivity of the surrounding structures also will affect the field. The magnet 22 is supported in the reaction chamber 21 of
A replaceable insert 77 of
In actual test runs for producing silver nanopowder, electrodes of silver having a 0.25″ diameter were used. The pulsed power supply 30 of
The replaceable insert 77 of
A dual magnet embodiment of the invention is illustrated in
A conducting wire 83 is connected to the negative output of the pulsed power supply 37 and to the negative terminal of solenoid magnet 82. A conducting wire 87 connects the negative terminal of the solenoid magnet 81 to the positive terminal of the solenoid magnet 82, thereby connecting the solenoid magnets in series. The solenoid magnets 81 and 82 in turn are held in place by mechanical struts 84 and 85 (which are physically connected to the interior surface of the reaction chamber 21), and by aluminum spacers 86 a and 86 b (which maintain the space between the magnets and maintain axial alignment of the principal axis of the magnets).
The operation of the embodiment of the invention as illustrated in
A replaceable shield 97 is placed on the face of the magnet near the gap between the electrodes 24 a and 24 b of
Typically, the replaceable shield is composed of a polycarbonate material which coats the nanopowder during the synthesis process and thereby reduces nanoparticle agglomeration.
As shown in
It is to be understood that instead of a solitary solenoid magnet embodiment of the invention as illustrated in
Although the preferred embodiments of the invention have been described in detail, various substitutions, modifications, and alterations can be made without departing from the spirit and scope of the invention as defined in the claims. By way of example, while the use of a magnetic field in accordance with the invention has been shown and described in connection with a radial gun form of a pulsed plasma system, the invention also is applicable to other plasma based systems. In a transfer arc system for synthesizing nanopowder, which includes a plasma torch and a single precursor member, the magnetic field could be applied around the precursor member in near proximity to the area of plasma interaction to increase the precursor material removal rate and thus nanopowder yield. Similarly, increased yield may be attained in a microwave system for synthesizing nanopowder by applying a magnetic field in near proximity to the area where plasma interacts with the precursor material.
While the preferred embodiments described above refer to a solenoid magnet containing an insert that may provide a precursor coating material that may interact with the plasma, it is to be understood that the same result could be obtained without an insert by using an independent source to feed precursor coating material for interaction with the plasma.
The above descriptions have been made by way of preferred examples, and are not to be taken as limiting the scope of the present invention as defined by the following claims.
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|U.S. Classification||219/121.36, 219/651, 219/121.59|
|International Classification||B01J19/08, B23K9/00, B23K10/00|
|Cooperative Classification||B22F9/14, B22F2999/00, B01J2219/0822, B01J19/088, B01J2219/083, B01J2219/0886, B01J2219/0809, B01J2219/0898, B01J2219/0839, B01J2219/0862, B01J2219/0854|
|Sep 24, 2003||AS||Assignment|
Owner name: NANOTECHNOLOGIES, INC., TEXAS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SCHRODER, KURT A.;JACKSON, DOUG K.;REEL/FRAME:014545/0323
Effective date: 20030924
|Sep 21, 2006||AS||Assignment|
Owner name: NOVACENTRIX CORP., TEXAS
Free format text: CHANGE OF NAME;ASSIGNOR:NANOTECHNOLOGIES, INC.;REEL/FRAME:018279/0850
Effective date: 20060707
|Aug 3, 2009||FPAY||Fee payment|
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|Apr 6, 2010||AS||Assignment|
Owner name: NCC NANO, LLC,TEXAS
Free format text: CHANGE OF NAME;ASSIGNOR:NOVACENTRIX CORPORATION;REEL/FRAME:024185/0480
Effective date: 20100401
|Sep 12, 2013||FPAY||Fee payment|
Year of fee payment: 8